On Parallels 9 I just updated a 10.9.2-VM to 10.9.3 using the downloaded DMG. The upgrade runs through no problem. The VM reboots. But the screen stays black and the VM is stuck after a while. Sorry, only now I saw this: http://forum.parallels.com/showthread.php?303168-Workaround-found-for-Black-Screen-on-Mac-10-9-3-Guest
Oh, sorry for the noise, I've seen only now http://forum.parallels.com/showthread.php?303168-Workaround-found-for-Black-Screen-on-Mac-10-9-3-Guest